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Why is a Random Orbital Sander...

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Forum topic by KnickKnack posted 09-02-2011 06:02 PM 1099 views 0 times favorited 14 replies Add to Favorites Watch
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KnickKnack

993 posts in 2313 days


09-02-2011 06:02 PM

...so called?

I’ve owned a goodly number of these things – I tend to buy the cheap ones for 15 euros or so and, when they die, which they invariably do, they simply give me a new one or my money back (if it’s within 2 years, which it usually is).

I’ve studied the outside and the insides, and watched them for hours and hours in action.

There’s nothing random about it, as far as I can tell – it goes in circles, always.
The only random thing I’ve ever seen a few of them do is to start making a bad noise, usually followed within a few days by complete outright catastrophic failure.

Do the expensive ones do anything random?
Did they originally do something random but don’t anymore?

Why?

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."


14 replies so far

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Bertha

12951 posts in 1440 days


#1 posted 09-02-2011 06:40 PM

They actually orbit on noncircular paths, so the orbits don’t overlap and make grooves. Someone with better physics can probably explain it better. I’ve got cheap ones and expensive ones. In my experience, until you get up to the Festools, they’re all pretty much the same. The Festool feels markedly different but you have to pay dearly for that feeling.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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CharlieM1958

15794 posts in 2965 days


#2 posted 09-02-2011 07:09 PM

Al, I have this bad boy that’ll take the siding right off your house. I haven’t put a lot of time on it, though, so I can’t speak to it’s longevity.

My experience with orbital sanders in fine woodworking is that you have to be very careful about moving up through the grits, or you’ll end up with those nasty swirl marks.

-- Charlie M. "Woodworking - patience = firewood"

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Bertha

12951 posts in 1440 days


#3 posted 09-02-2011 07:46 PM

That Bosch is pretty handsome. I sprung for the Festool a while back but my DeWalt 5” still gets a lot of work. What does Bosch want for that devil?

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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Loren

7822 posts in 2395 days


#4 posted 09-02-2011 07:57 PM

I have both the older Festool and the newer rotex that looks like the Bosch
(same factory line? I’ll bet). While cruder and less convenient to switch between
modes, I think the older one is the better tool.

-- http://lawoodworking.com

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Sawkerf

1730 posts in 1815 days


#5 posted 09-02-2011 08:02 PM

My DeWalt ROS isn’t actually “random”, but has two rotations. One is just the disc spinning around the midpoint, and the second is the midpoint also rotating around another point. The two motions do a great job of eliminating “swirl” marks.

-- Adversity doesn't build character...................it reveals it.

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PurpLev

8476 posts in 2395 days


#6 posted 09-02-2011 08:27 PM

the ‘random’ isn’t about the sanding pad moving randomly, but refers to the scratch/sanding marks that the sander leaves which are not perfectly round as the sanding pad rotates off center (as was stated a few comments above). the idea is that this makes the scratch marks less noticeable.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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Bertha

12951 posts in 1440 days


#7 posted 09-02-2011 08:33 PM

I seem to use these things less and less. I’m more of a handplane-after-the-planer guy and I usually just grab a sanding block. I actually probably use a powered pad sander more than the ROS. I’ve got a $10 pneumatic one that I really like. It looks like a bug, which is probably the only reason I like using it. Well, that’s not true…I love the switches on pneumatic equipment.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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CharlieM1958

15794 posts in 2965 days


#8 posted 09-02-2011 08:52 PM

Al, I think I paid $200. I wanted something just a little less aggressive than a belt sander for certain situations. Most of the time, though, I’m using on of my smaller 5” sanders. The Bosch really takes two hands to control.

-- Charlie M. "Woodworking - patience = firewood"

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Bertha

12951 posts in 1440 days


#9 posted 09-02-2011 09:11 PM

I totally understand. My belt sander was like $30 and has like 30-grit paper on it. It will destroy anything that gets near it. If it can’t destroy it, it will destroy itself, sending shredded paper flying. I still want one of those tiny little VW-bus-looking Bosch belt sanders. Word on the streets is that they’re crap, though.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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mailee

44 posts in 1225 days


#10 posted 09-02-2011 09:25 PM

I use my Metabo random orbital sander regularly and although it wasn’t cheap it is a great piece of kit. I have had it for about 5 years now and just renewed the brushes in it. It also has two settings for the orbit, one for fast removal and the other which is smaller for fine finishing.

-- www.alanwilley.co.uk

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Grandpa

3204 posts in 1422 days


#11 posted 09-03-2011 12:25 AM

I still use a PC 505 pad sander that uses a half sheet of paper. It is an orbital sander but not a random orbital. I don’t plan to change until I wear it out and I am not sure one person can do that. The main difference I find between cheap sanders and more expensive sanders is the orbits per minute. The cheap sanders run at approximately half the speed of the better sanders. I always found that this allowed the sander to grip the wood and “park” while the machine shook me. I would swell and get numb. The better sanders run much faster and they feel like they float on the wood. My PC runs at 10,000 orbits per minute. They don’t cause the swelling and numbness in my hands. When I find something I like I stick with it…..like some folks still using hand planes….LOL

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cloakie1

204 posts in 1302 days


#12 posted 09-03-2011 12:35 AM

i have a pneumatic shanano orbital palm sander…was 600 nz$ when i bought it 6 years ago and it is brilliant to use. the trigger gives you complete control over the speed as well as a regulator switch underneath to control it’s power…altho i prefer it to have everything an regulate with the trigger. something you can’t do with electric ones i have a stick on pad which means even sanding but the downside is changing grits becauser the disks are only onecers where as the velcro backs you can get more life out f the disk…depending on the work load

-- just get stuck in and have a go!!!

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a1Jim

112862 posts in 2324 days


#13 posted 09-03-2011 12:41 AM

I have about seven different brands of ROS I find they differ in what the sanding patterns are . Some are more aggressive then others . I had used an inexpensive ROS for years even though they where much better then a pad sander they tended to run rough and cut very aggressively. I found spending a little more allowed for a much better sander that ran smoother and lasted longer. My favorite is a Milwaukee which turns out to be mid range I think around $70.

-- http://artisticwoodstudio.com Custom furniture

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KnickKnack

993 posts in 2313 days


#14 posted 09-04-2011 08:12 PM

Thanks to everyone for the, as usual, learned discussion – I think we agree that the random isn’t actually random.
I think I also failed to appreciate that there was more to a (Non-)ROS that just doing a bit of shaking about.
Next time I’m visiting a more consumer-oriented country than Portugal (ie somewhere where you can buy a somewhat larger range of tools) I’ll try and have a play (or at least a feel) with some of these “bad boys”.
Thanks again to all

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

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